John Hartson helped himself to a fantastic festive hat-trick as the champions turned up the heat on Rangers at the top of the Scottish Premier League.

Mark de Vries had threatened to gatecrash Celtic's Christmas party by firing an in-form Hearts side in front and on level terms during an epic six-goal cracker at Parkhead.

But the man-of-the-match Welshman pounced in some style before Henrik Larsson added another which was harsh on the visitors - who had played more than their part.

The result saw Celtic close the gap on Rangers to one points, but things did not start too well for Martin O'Neill's men as they suffered a blow just seconds before-kick-off when number one Robert Douglas seemed to sustain a hamstring injury in the warm-up.

The Scotland star, who must also have a hernia operation in the New Year, was replaced in goal by Magnus Hedman for his first start since September 1.

And Larsson almost settled them down within minutes of the start when he was played through by Hartson, but his deflected right-foot shot went inches past the post.

That would have been a perfect start for Hedman, but the first thing he did was pick the ball out the back of his net after Hearts took a shock lead after just three minutes.

Steven Boyack, who himself has been plagued by injuries, whipped in a decent cross and De Vries got away from his marker and headed home past the Swede from six yards.

The home side looked rattled at the back every time Hearts attacked and De Vries was desperately close to getting on the end of another Boyack cross at the far post.

But in attack Celtic always looked dangerous and the visitors needed a great save from Roddy McKenzie to stop Larsson from equalising in the 14th minute.

The Swede did put the ball in the back of the net moments later when he headed Paul Lambert's cross emphatically into the corner of the net, but the celebrations were cut short by the linesman who controversially flagged for off-side.

The home defence were again in disarray in the 19th minute as Phil Stamp's deflected right-foot shot flew past the post after De Vries had teed him up on the edge of the box.

Celtic continued to push for a goal, but McKenzie again thwarted them with a point-blank save from Bobo Balde's header after being picked out by Alan Thompson.

The goalkeeper, however, could do nothing to stop his side going level in the 22nd minute when Hartson was on hand to convert one of his easiest goals.

Thompson curled in a left-foot corner and the Welshman was left all alone in the six-yard box to head the ball into the back of the net.

Referee Hugh Dallas continued to frustrate the home crowd with some strange decisions, but he had no alternative but to book Austin McCann for crudely cutting down Larsson.

Hartson should have put Celtic ahead in the 35th minute when he miss-kicked Sutton's pull-back after good work from Thompson.

Hearts seemed to respond again and Kevin McKenna was presented with a free header from six yards out, but somehow headed Jean-Louis Valois corner over the crossbar.

But the visitors paid a harsh price for that missed chance as Hartson bagged his 16th goal of the season just before the break.

Petrov squeezed the ball through to him and with the Hearts defence appealing for off-side he coolly rounded the keeper to slide the ball into an empty net.

Celtic looked to kill the game off early in the second-half and McKenzie again did well to keep out Larsson's header from Thompson's cross.

Hartson failed to react quickly enough on the rebound and his effort was also turned away, but the Welshman was again looking for his hat-trick in the 53rd minute when he controlled Lambert's pass before clipping a right-foot effort just over the bar.

But the visitors came back strongly again and they will wonder how they failed to level the scores in the 55th minute as efforts from Neil MacFarlane, Valois and McKenna were all somehow kept out as Celtic survived a bizarre goalmouth scramble.

Larsson came within inches of doubling Celtic's lead in the 65th minute when Hartson and Petrov combined well to give him a chance, but his chip went just past the upright.

The Celtic supporters were celebrating moments later when news filtered through from Fir Park, but that seemed to distract the home side as Hearts stunned them into silence with the leveller.

Valois and Boyack linked up well and De Vries sprung the off-side trap before firing low past Hedman.

But in an amazing couple of minutes, the game changed again when Hartson bagged his hat-trick in sensational style.

The striker hit a brilliant right-foot volley from Thompson's cross past McKenzie and into the bottom corner.

That knocked the stuffing out of the visitors and Larsson killed them off in the 72nd minute when he coolly rounded McKenzie before sliding the ball into an empty net.

Celtic were threatening to run riot as Sutton's header was cleared off the line, but that would have been tough on the Edinburgh men - who had come up against a man in hot form. Rangers beware.

Teams:

Celtic Hedman, Valgaeren, Balde, Laursen, Agathe, Lambert, Sutton, Petrov, Thompson, Larsson, Hartson.

Subs Not Used: Maloney, Mjallby, Smith, Crainey.

Booked: Thompson.

Goals: Hartson 22, 44, 68, Larsson 73.

Hearts McKenzie, Maybury, McKenna, Pressley, McCann (Mahe 82), Weir, MacFarlane (Hamill 79), Stamp, Boyack (Simmons 74), Valois, de Vries.

Subs Not Used: Gordon, Severin.

Booked: McCann.

Goals: de Vries 4, 66.

Att: 58,450

Ref: Hugh Dallas (Scotland).